Keep your expectations reasonable. The EPI springs aren't going to turn the Mule into a super quick machine. It will just make it more responsive and quicker than stock, especially on trails with a lot of tighter turns that require the vehicle to slow down, and then have to get back up to speed. Worth it to me for the small price.
The only mods I've done are:
-Aluminum skid plate (a must if doing rough trail riding. I've high centered/scraped so many times I obviously needed a lift.)
-Highlifter (see above)
-CV Joint/A-arm guard sets. From ebay, but I actually like Kawasaki's better, more coverage, but 50% more expensive.
-Wheel spacers after lift
-Aluminum roof. DIY. So much cheaper than buying them after market, but those are nice.
-Under seat storage mods. Both the raised center bin and a drop-in garbage can that rests on the side skids.
-NOAM Bluetooth and speakers
-Dynamat and hoodliner under the lift-bed. Cuts down the engine noise/echo and bed vibrations. Can have a normal conversation with passengers at speeds without having to yell.
-fabric seat covers. Good for summer heat.
-Hood Scoop. Worked fantastic this weekend with mid-90's. No heat in the cab at all after running all day
-Swap out 12-volt cig lighter receptacle for USB charger w/voltmeter:
-UNI Air Filter
Mods still need to do:
-Hinged seat mod. How in the world Kawasaki doesn't have a hinge on the front seat is baffling to me.
-new tires, perhaps ITP Blackwater or Tusk Terabite, maybe wheels, but they aren't needed yet.
-maybe swap out non-LED OEM lights